As is known, the human or animal body has an extensive network of blood vessels including both the venous and arterial systems for circulating blood throughout the body as a whole as well as the organs of the body.
In recent years, a variety of traumatic surgical procedures have been replaced with procedures that involve the use of one or more catheters being advanced through the vascular system of the body to gain access to diagnose and/or treat issues involving the vasculature of a particular organ. For example, strokes (e.g. ischemic strokes caused by blood clot blockages in the brain); coronary artery blockages within the heart; and various heart defects may be treated by advancing catheters to the affected site where various procedures can be initiated to treat the problem. Stents have also been deployed via a catheter where such stents are positioned using catheters at a location where intervention is required. Other catheter procedures are also done in many parts of the body including leg vessels, renal arteries etc. as well as many other complex vascular percutaneous vascular procedures including for example treatment of valvular heart disease, aortic dissections, dysrhythmias, management of shunts for dialysis patients. Similarly complex aneurysms in the brain and other locations are increasingly being treated through a percutaneous endovascular route.
In order to effectively use catheters within the body to complete a medical procedure, generally the catheters must be flexible enough to follow through the tortuous curves of the body's vascular system whilst being stiff enough to hold position (e.g. when the interventionist passes additional tools through the catheter).
If the catheter is too flexible, the catheter may fall back into other vessels within the vascular system. If the catheter is too stiff, it may cause damage to the surrounding tissue as it navigates around corners of the vessels, if it is able to be moved at all and/or may cause significant time delays in completing the medical procedure. In certain procedures, such as endovascular interventions to remove a blood clot from the brain of a patient who has had an ischemic stroke, “time is brain”, meaning that delays in completing a procedure can significantly affect the outcome for the patient.
Also, the degree of tortuousity within blood vessels as well as the stiffness of vessels increases with age due to multiple factors including atherosclerotic disease, loss of height of the spine, etc. With the aging population and improving technologies, more and more of these procedures are being done in an older population necessitating access despite the increased complexity of conducting procedures through tortuous and/or stiffer vessels.
Further still, there are significant variations in the vascular anatomy of different patients, FIG. 1 shows a typical aortic arch 179 and the connecting vessels in a human. The aortic arch 179 is connected to the ascending aorta 178 and the descending aorta 180. The ascending aorta is connected to the right and left coronary arteries 171, 172. The aortic arch is connected to the brachiocephalic artery 173 which splits into the right subclavian artery 174 and the right common carotid artery 175. Also connected to the aortic arch are the left common carotid artery 176 and the left subclavian artery 177. As noted, the figure shows a typical aortic arch but it will be appreciated that the precise connections and form of the vessels may vary from patient to patient. For example, in some patients, the left common carotid artery may arise from the innominate artery (this variant is called a bovine arch). In this situation the angle between the descending aorta and the left common carotid artery is more acute making the catheterization more challenging.
To take a typical catheter procedure as an example and as described in more detail below, to access the blood vessels in the head, the interventionist typically navigates a catheter system up the descending aorta 180 from the femoral artery and into the aortic arch 179 and into the left common carotid artery 176. For the purposes of the description herein a “catheter system” implies various combinations of inner catheters (eg. diagnostic catheters, guide wires, microcatheters) and outer guide catheters (eg. distal access catheters and balloon guide catheters) where the inner and outer components are substantially coaxial and can slide over or within the other. This can include coaxial, triaxial and rarely quadra-axial procedures. In most circumstances, the components will move together with a guide wire usually extending beyond the outer guide catheter and inner components such as a diagnostic or microcatheter. Hence, the catheter system may be both a combination of a wire within the catheter during antegrade movement of the catheter system but may also mean just the catheter without the wire. Antegrade movement is generally conducted by a combination of advancing the guide wire followed by advancing the catheter over the wire all of which may involve twisting or turning the catheter and wire in order to turn the distal end of the guide wire and catheter into the appropriate vessel. After reaching the aortic arch, for example, the catheter system is navigated up the left common carotid artery 176 and into the left internal carotid artery. Depending on the underlying condition and the procedure being conducted, at this stage the interventionist may utilize a variety of different catheters (including microcatheters and microwires) and techniques to gain access to intracranial vessels and ultimately to the site where the procedure is to be conducted.
As FIG. 1 indicates, the vascular system comprises complex junctions in which a number of vessels intersect. In addition, older people often have increasing tortuosity and/or stiffness of their vessels and also the vessels may become longer. A catheter system which is too stiff can straighten out tortuous vessels (which may or may not be advantageous) and/or produce damage to the vessel as it is being navigated through a tight curve. However, if the catheter is too flexible, it may not be able to maintain its position within the vessel and, for example, fall back into the aortic arch after it has been successfully guided into the left internal carotid artery (especially as further catheters and tools are being advanced through the catheter to enter the brain vessels and/or as the guide wire is withdrawn). In some cases additional catheters face friction as they are being advanced and as such, this creates a backward force on the guiding catheter hence preventing the interventionist from completing a procedure and/or wasting time in removing a catheter and selecting and navigating a different catheter into position.
Catheter Design and Performance
As noted above, two classes of catheters used in cerebral procedures are diagnostic and guide catheters. Diagnostic catheters are generally those used to gain access to an area of interest whereas guiding catheters are used to support and guide additional equipment including diagnostic catheters, guidewires, balloons, other catheters etc. as may be required for a particular surgical technique.
Typical diagnostic catheters will range from 4 F to 6 F (French) and have lengths of 65-125 cm. They may have braided wall structures and they will generally have a soft tip with a range of shapes formed into the tip.
Guide catheters are generally larger (eg. 6-8 F) and are 80-100 cm in length. They generally have reinforced construction with a significantly stiffer shaft to provide back-up (i.e retro) support for the advancement of any additional equipment as mentioned above.
From an anatomical perspective, catheters generally pass through different zones of the vasculature, namely the abdominal and thoracic vasculature between the femoral artery and aortic arch (approximately 50-75 cm), the cervical vasculature (approximately 15-20 cm) and the cephalic/cerebral vasculature (approximately 10-15 cm).
Various properties and geometries may also be engineered into both diagnostic and guide catheter including:                a. Trackability—the ability of the catheter to slide over a guide wire particularly through tortuous (tightly curved) vessels.        b. Pushability—the ability to advance the tip or head of the catheter based on the input from the operator from the hub (i.e. from outside the body).        c. Torquability—the ability to steer the tip of the catheter based on twisting at the hub by the operator.        d. Tip or head shape—the shape of the tip or head of the catheter will assist the operator in navigating the distal tip of the catheter through particular anatomical features. For example, a catheter may have a flush, straight, simple curve, complex curve, reverse curve or double curve shapes inter alia. Such shapes may be categorized as simple or complex.        
In particular, diagnostic catheters are provided with a wide range of tips having the above shapes to allow the surgeon a choice of tip shape when conducting a procedure mainly to address variations in a patient's anatomy.
Catheter Construction
Each catheter may be constructed from a plurality of materials, having various structures and/or layers within the catheter wall structure to give the catheter particular properties or functional characteristics. These may include:                Surface Coatings—Surface coatings desirably reduce thrombogenicity, have low friction coefficients and/or anti-microbial characteristics.        Reinforcement—Internal wire braiding is used to impart torque control/stiffness characteristics to the catheter.        Polymer Layers—Different polymers may be used to give different structural characteristics to the body of the catheter. For example,                    Polyurethanes can be soft and pliable and hence follow guide wires more effectively. However, they have a higher coefficient of friction.            Nylon may be used for stiffness and be able to tolerate higher flow rates of fluids through them.                        
The choice of a particular catheter or system of catheters may be determined by the skill and experience of a particular surgeon.
Some typical properties of different catheters are summarized in Table 1.
TABLE 1Summary of Catheter PropertiesTypical TipCatheterBody PropertiesDiameterTypical LengthFeaturesGuideUsually quite6-8FExtracorporeal +May haveCatheterstiffGroin toballoonAtraumatic tipCarotidSupports and80-100 cmguides othercathetersDouble lumenif BalloonGuideCatheter(BGC)DiagnosticVariable Tip4-6FExtracorporeal +Soft TipCatheterStiffnessGroin toMultipleVariable TipCarotidShapesShapes100-125 cmTorquableMicrocatheterSoft Tip1-5-2.5fGoes throughRoundedPushablethe guideSoft TipTrackablecatheterTravel tointracranialvessels (over amicrowire) andto beyond theclot.150 cmGuide WirePushable1FTravels insideRoundedTorquableof diagnosticcatheter orguide catheter(used toadvance thesecatheters to thecervical carotidartery)150-300 cmReperfusionMultizone4-6FTravel insideRoundedCatheter(may be up to(diameterthe guideSoft Tip12-15 zones)may becatheter.ChallengingIncreasingmoreUsually over adesign tolevel ofproximallymicrocatheterpreventsoftnessto allow forExtracorporeal +ovalizationdistally tobetterGroin toduringallow thesuction.Occlusionpassingcatheter to105-125 cmthroughnegotiatesignificantsignificantcurvature andtortuousitywhileand remainapplyingatraumaticsuction.Distaltransitionzones mayextend for 30-40 cm)Enables two-way FluidFlowPushableStentIntegratedvery smallExtracorporeal +IntegratedClot Retrievalin itsGroin toClotSystemcollapsedOcclusionRetrievalPushablestate (travel180 cmSystemthroughTravel throughmicrocatheter).microcatheter.Inexpandedstate: 3-6 mmMicrowirePushable180-200 cmextracorporealround softTorquabletravelsto intracraniallytip.10-16/1000 ofthrough(beyond thean inchmicrocatheterclot)softatraumatic tipTypical Endovascular Procedures for Treatment of Ischemic Stroke
As noted above, when an endovascular surgeon begins a procedure, access to the vasculature is typically obtained through the groin. After groin puncture, a variety of the following steps are performed to advance different catheters through the vasculature to a site of interest. Typically, in the case of a procedure using a balloon guide catheter and stent (i.e a clot retrieval device), these steps include:
Step A—Aortic Arch Access
                a. Following groin puncture, a sheath is deployed. The sheath acts as an access port to the body and will be inserted about 5 cm of a typical 15 cm length into the femoral artery. The sheath has an ID of approximately 8 F.        b. An assembly of a balloon guide catheter (BGC), a diagnostic catheter (DC) and guide wire (GW) is advanced to the aortic arch. The BGC will typically have an OD of 8 F. The DC (OD 4-6 F) is retained inside the BGC and the GW (OD 0.035″) is retained within the DC.Step B—Carotid and Cerebral Artery Access        c. The DC is manipulated to gain access to the desired carotid artery.        d. After gaining access to the carotid artery, the GW is advanced, typically up to 20-30 cm towards the occlusion site (but within the cervical carotid arteries).        e. After the GW has been advanced (or concurrently and/or sequentially), the DC is advanced over the GW to gain access to the occlusion site. This may occur in a concurrent and/or sequential process depending on the particulars of a particular patient.Step C—Balloon Guide Catheter (BGC) Placement        f. The BGC is advanced over the DC and GW to also gain access to a straight segment of the cervical internal carotid artery.        g. The DC and GW are then fully removed.Step D—Microcatheter/Microwire placement        h. A microcatheter (MC) and microwire (MW) are advanced together through the BGC all the way to the clot such that the distal tip of the MC and MW are positioned just past the distal edge of the clot.        i. Once the MC is positioned, the MW is removed.Step E—Stent Deployment        j. A stent (i.e. clot retrieval device) is advanced through the MC until the distal tip of the stent is adjacent the distal end of the MC.        k. The stent is unsheathed by pulling back on the MC while holding the stent in position. As the stent is unsheathed it will expand into clot to engage with the clot.Step F—Clot Removal        l. The BGC is inflated to stop antegrade flow and retrograde flow (suction) through the BGC is initiated.        m. Simultaneously, the stent which is now engaged with the clot, together with the MC is pulled proximally through the BGC to outside of the body.        n. A check angiogram is performed through the BGC to see if the clot retrieval has been successful. If not the steps j-m may be repeated again.        o. Once successful reperfusion has been achieved the BGC, stent and clot are removed from the body.Variations        
In variations of the procedure, a distal access catheter (DAC) (4-6.5 F) may be added to the procedure. This can be done one of two ways                a. Aspiration technique.                    i. In this technique, after access to the cervical internal carotid artery has been achieved using a guide catheter and DC, the guide catheter (GC) which is not a BGC (i.e a DAC) is placed in the cervical internal carotid artery.            ii. The DC is removed            iii. A tri-axial system consisting of a DAC, a MC and MW are advanced towards the intracranial circulation with the aim of having the tip of the DAC (Aspiration catheter) reach the face of the clot. For achieving this it is possible that the MC and MW may have to be placed beyond the clot.            iv. The MW and MC are removed.            v. With the DAC at the face of the clot, suction through the DAC is applied until there is successful retrieval of clot or the endovascular surgeon decides to try an alternative approach. Local suction has an advantage that more of the suction pressure is likely to be transmitted to the clot.                        b. Solumbra technique                    i. The initial part of this technique is the same as the Aspiration technique (i.e steps a(i)-a(iii)).            ii. However once the MC is beyond the clot and the DAC is at the face of the clot, the MW is removed and a stent is deployed across the clot.            iii. Then, while applying suction to the DAC, the MC and stent are withdrawn. Thus, the suction pressure is right next to the clot rather than from the neck as with a BGC. Also, the stent enters the DAC while still in the intracranial vessels thus reducing the likelihood of losing the clot once it has been captured.                        
In cases where the aspiration techniques without using a stent are not successful in removing the clot, with a BGC in place, a GW, MC and stent may be subsequently deployed.
Importantly, during any procedure the physician must carefully balance differences in the various geometrical and physical parameters of the catheter system against the 3 dimensional geometry of the patient's vasculature. That is, the physician must consider, for example, the shape of the distal end of the diagnostic catheter system with the understood geometry of the patient's vasculature, the stiffness of the guide catheter as well as the procedural objective of the catheter system as a whole.
Generally, a variety of diagnostic catheters are available to the physician where a particular diagnostic catheter is chosen depending on the route desired and the location of the issue. While a physician may have a significant number or library of diagnostic catheters available to him/her for a particular procedure, the selection of a particular catheter will often be based on the physician's experience and/or interpretation of the patient's vasculature from diagnostic and/or imaging results. As noted above, other factors, including the patient's age and size may also be considered. For example, when considering the imaging data, the physician may interpret particular features of the image that suggest the use of one diagnostic catheter design over another. That is, to the skilled eye of the physician, imaging data may reveal a degree of tortuosity with the vasculature that would suggest using a guide catheter having a more flexible region to enable navigation around a particularly tight curve to avoid the time delays that may result if a guide catheter that is too stiff is selected. However, a guide catheter that is too flexible may present problems during the procedure if it is unable to properly support microcatheters, microwires and other equipment within it for subsequent steps of the procedure. Further still, as shown in FIGS. 2A and 2B, different tip shapes of a DC can be selected which are ideally matched to the shape of the patient's vasculature in order that the interventionist can “hook” the vessel of interest with the appropriate DC. As can be appreciated, the ultimate success and speed by which a physician can place the DC is the result of various factors including balancing the degree of forward push, the torque applied to the DC and the selection of the right device against the actual anatomical factors. Importantly, throughout the process various complexities can occur where the DC does not go into the vessel of interest but ends up somewhere else.
As such and as can be appreciated, training to become skilled at catheter placement is an involved process requiring many hundreds or thousands of hours of practice, mentoring and exposure to a wide range of patients and their respective anatomies whilst carrying out a wide range of procedures. However, the process of medical training is a process of graded responsibility wherein senior established physicians slowly allow trainees to do increasing amounts of patient management. However in the case of many emergencies, particularly those that are as emergent and complicated as acute stroke, there are limitations in terms of how much opportunity a trainee gets. As a result, while medical trainees may be exposed to complicated procedures, the amount of hands on experience they acquire during these emergencies may take many years to acquire.
Furthermore, in the case of acute stroke, it is well accepted that ‘time is brain’ with there being clear data to support that the faster the brain is repurfused, the higher the likelihood of a better outcome for the patient. As such during the management of an acute stroke, all the steps of recanalization described above should be conducted as fast as possible. This includes imaging, image processing, diagnosis, patient preparation, and the actual steps of a procedure.
Training systems exist that can assist the physician in developing their skills including simulation systems that interface physical manipulation of a real proximal end of a catheter system to a simulation of the distal end within a simulated vasculature. Such systems, for example, as described at www.mentice.com, provide physicians an effective way of developing manual manipulation skills and experience with a simulated system which can significantly improve skill levels prior to real-world procedures on patients.
While effective, current simulators are limited in that while they simulate “real” patient anatomies, derived from real imaging data, they do not represent the anatomies of an actual patient who is in immediate need of a procedure. That is, while current simulation systems allow physicians to practice on simulated patients, they are not actual patients whose specific anatomies are before them. Moreover, while a physician may be able to practice on various simulated patients with known variations and complexities in their anatomy, such practice may have become dated by the time an actual patient presents having a particular anatomy. That is, it may have been months or years since the last time a physician practiced on a particular anatomy.
The inventor's papers (incorporated herein by reference) “Analysis of Workflow and Time to Treatment on Thrombectomy Outcome in the Endovascular Treatment for Small Core and Proximal Occlusion Ischemic Stroke (ESCAPE) Randomized, Controlled Trial” (Circulation. 2016; 133:2279-2286. DOI: 10.1161/CIRCULATIONAHA.115.019983) and “Analysis of Workflow and Time to Treatment and the Effects on Outcome in Endovascular Treatment of Acute Ischemic Stroke: Results from the SWIFT PRIME Randomized Controlled Trial” (Radiology; 2016) discuss the variances in different steps of the workflow from the onset of an ischemic stroke to completion of recanalization procedures. As shown from these studies and as shown in Table 2, there is significant variation in the time that a surgeon may spend to complete a recanalization procedure.
TABLE 2Interval Times in the Workflow of the ESCAPE TrialMedian,InterquartileWorkflow Time IntervalsN*minRangeStroke symptom onset to arrival in308107.549.5-224 emergency department ofendovascular-capable hospitalStroke symptom onset to qualifying CT311135 76-244Stroke symptom onset to randomization314174119-285Stroke symptom onset to first reperfusion145241176-359Arrival in emergency department of3111911-29endovascular-capable hospital toqualifying CTQualifying CT to groin puncture1615139-68Groin puncture to first reperfusion14430  18-45.5
From these studies, variances in the time to complete particular steps can be attributed to different factors including the skill and experience of the surgeon, the equipment that may be used and the anatomy of the patient. Thus, to the extent that resources are available that enable the training of surgeons, the identification of equipment that may be most appropriate for a particular patient and/or recognition of particular characteristics of a patient's anatomy, time to reperfusion can be reduced and/or the variances in these times on a wider scale can be reduced or improved.
Accordingly, there has been a need for systems and methods that address these problems and more specifically for systems and methods that improve the skills and decision making of surgeons. Moreover, there has been a need for providing a personalized solution for the surgeon to practice on the actual patient that, within a few minutes, they will actually be conducting a procedure on. That is, there is a need for systems that utilizes CT scan and/or other imaging data obtained from a patient during a diagnostic phase that can be used within a simulator while a patient is being prepared for an endovascular procedure in order to assist the surgeon in pre-selecting specific catheters/equipment for a procedure, whilst also enabling them to practice the placement of selected catheter equipment within that specific patient's anatomy.
Furthermore, there has been a need for systems that, based on the specific anatomy of a patient, suggests and/or selects one or more recommended pieces of equipment having knowledge of the procedure about to be performed and a library of available equipment.
Further still, there has been a need for systems that based on the specific anatomy of the patient, suggest alternate techniques based on historical data if the geometry/characteristics of a particular anatomy has been shown in the past to be problematic to one particular procedure.
Further still, there has been a need for systems that based on the experiences of physicians conducting procedures using particular catheters within particular anatomies can recognize past situations and provide tips or insights to a physician when they are conducting a procedure which presents circumstances similar to a previously conducted procedure.
Further still, there has been a need for systems that can utilize the data of past procedures to assist in the design of future equipment having consideration to procedures that may have experienced problems.
Further still, there has been a need for systems that allows the manufacturers of catheters and wires to test their products against various anatomical variations to design and improve their products.
Further still, there has been a need for systems that can allow a physician to record an actual procedure and feed it back into a simulation system having an interactive environment to understand how procedures could be done differently or better.